Efficacy of Zinc Phosphide and Strychnine for Black-Tailed Prairie Dog Control

Abstract

Three rodenticide treatments, zinc phosphide (prebrited) and strychnine (both with and without prebrit), were evaluated immediately following treatment for efficacy of controlling bircktailed prairie dogs in western South Dakota. Active prairie dog burrows were reduced 95% with zinc phosphide, 83% with strychnine (prebaited), and 45% with strychnine without prebait. Zinc phosphide was the most effective in reducing active burrows of prairie dogs. The black-tailed prairie dog (Cynomys ludovicianus) inhabits prairie regions of the western United States from Canada to Mexico, east of the Rocky Mountains and west of the tall grass prairie (Hal1 198 1). Prairie dog towns often encompass vast areas. Because prairie dog feeding and burrowing activities conflict directly with interests of ranchers and range managers, widespread control programs using rodenticides were begun in the late 1800’s on the Great Plains (Merriam 1902). Prairie dogs are still considered a problem when they compete with cattle for forage plants (Hansen and Gold 1977). Most recent prairie dog control programs on federal, state, and private lands consist of poisoning prairie dogs with zinc phosphide on rolled oats after prebaiting with rolled oats (Schenbeck 1982). Zinc phosphide has been widely used as a rodenticide since 1942-43 when strychnine supplies became limited during World War II (Timm 1983). More recently, zinc phosphide formulation and application rates have been developed for use in prairie dog control (Tietjen 1976). Strychnine has been used for prairie dog control since the late 1800’s (Merriam 1902). These two rodentitides are widely used for prairie dog control throughout the western United States. However, comparative information of these two rodenticides for effective control of black-tailed prairie dogs has not been reported. This investigation was undertaken to compare the efficacy of rodenticides zinc phosphide (pre-baited) and strychnine with and without prebaiting for controlling black-tailed prairie dogs in western South Dakota. Study Area